磷钨酸（英语：Phosphotungstic acid），简称PTA，英文名称也作tungstophosphoric acid，简称TPA，是化学式为H₃PW₁₂O₄₀的杂多酸，平常会以水合物的形式出现，EPTA是磷钨酸乙醇溶液的简称，常用在生物学中。磷钨酸为小颗粒，灰色或浅黄绿色的晶体，熔点为89 °C（24 H₂O的水合物），磷钨酸可溶于水（200 g/100 ml），水溶液呈无色。磷钨酸没有显著的毒性，是有微酸性的刺激物。

磷钨酸的离子中含有12个钨原子，一些早期的研究者不晓得其化学结构，例如生物化学家吴宪， 称其为磷-24-钨酸，化学式为3H₂O.P₂O₅ 24WO₃.59H₂O，(P₂W₂₄O₈₀H₆).29H₂O，其中钨、磷和氧的数量有误，但比例是正确的，一直到1970年代还有论文用到此不正确的化学式。

Phosphotungstic acid (PTA), tungstophosphoric acid (TPA), is a heteropoly acid with the chemical formula H₃PW₁₂O₄₀. It is normally present as a hydrate. EPTA is the name of ethanolic phosphotungstic acid, its alcohol solution used in biology. It has the appearance of small, colorless-grayish or slightly yellow-green crystals, with melting point 89 °C (24 H₂O hydrate). It is odorless and soluble in water (200 g/100 ml). It is not especially toxic, but is a mild acidic irritant. The compound is known by a variety of different names and acronyms (see 'other names' section of infobox).